308 BACTERIOLOGY OF THE EYE 



border then disappears (according to Saemisch, this begins at its upper 

 edge), and the ulcer clears. 



(The common histological peculiarities of a purulent keratitis in 

 man will not be discussed here.) 



It is a peculiar fact that a typical ulcus serpens has almost never been found in 

 a child. Augstein described a typical case with Pneumoccoci in a child of six 

 years. The chief reason for this is that lacrymal troubles are much rarer in them 

 than in adults. Whenever pneumococcal infection of the cornea has been observed 

 in children it has taken the form of keratomalacia, and has occurred in ill-nourished 

 infants (E. von Hippel, Knaebel, Braunschweig, Doetsch, Macnab 1 ) in atypical 

 ulceration after measles (Hertel), with an exceptionally severe conjunctivitis in the 

 new-born (Gasparrini), or in very severe pseudo - membranous conjunctivitis 

 (Beckers). 



Duane and Hastings state that Staphylococci are especially important in the 

 ulceration of the cornea which occurs in catarrhal conjunctivitis. There is no 

 proof that such is the case. 



In an ulcus corneae serpens the Pneumococci mostly lie in the yellow 

 progressive margin, amongst the infiltrating leucocytes. If material 

 be taken from this situation, they are found in the smear in large 

 numbers, and with evident capsules. The cultures are characteristic 

 of the Pneumococci found in other places, and agree with them in every 

 respect ; there is the same difficulty in their culture. Their patho- 

 genicity is generally not great in culture. Uhthoff and Axenfeld came 

 to the conclusion that a diminution of virulence must be presumed to 

 have occurred in these pyogenic Pneumococci. Homer agrees with 

 this for the majority of cases, but considers that the factor of adapta- 

 tion must be considered. 



The final proof of the identity of the Pneumococcus of ulcus serpens 

 with that of croupous pneumonia is furnished by Romer, who suc- 

 ceeded, by the action of the first organism, in making susceptible 

 animals immune to the latter. 



A keratitis can be produced in the cornea of the rabbit, the intensity 

 of which will vary, according to the quantity and the virulence of 

 the material introduced, from a severe hypopyon-keratitis to a 

 simple infiltration (Gasparrini, Cuenod, Uhthoff and Axenfeld, Bach, 

 Noeldeke, De Schweinitz, Yeasy, Augstein); a typical ulcus serpens 

 has never been produced. Uhthoff and Axenfeld once obtained a 

 peculiar interstitial ring infiltration, but this was not typical. On the 

 other hand, Romer obtained a typical ulcus serpens in apes. 



Romer has undertaken comprehensive tests to produce, by means 



1 In Braunschweig's and in Doetsch 's cases Slapliylococci and Streptococci were also- 

 present. 



